What is a wrong exhaust pipe

Exhaust too loud? Attention, measurements are often wrong!

So, did some research:

97/24 / EG - extract:

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2.2. Noise of the motorcycle at a standstill (conditions and measurement methods for checking vehicles in traffic)

2.2.1. Sound pressure level of the motorcycle in the near field

In order to facilitate a later check of the noise development of motorcycles in traffic, the sound pressure level in the vicinity of the mouth of the exhaust system must also be measured in accordance with the following provisions and the measurement result must be entered in the test report for the document according to Appendix 1B

2.2.2. Measuring device

A precision sound level meter according to 2.1.2.1 is to be used.

2.2.3. Measurement conditions

2.2.3.1. Condition of the motorcycle

Before starting measurements, the motorcycle engine must be brought to normal operating temperature. In the case of automatically controlled fans, the automatic switch must not be intervened in during the noise measurement.

During the measurements, the gearbox selector lever must be in neutral. If it is not possible to interrupt the power transmission, the drive wheel of the motorcycle must be allowed to run freely, for example by jacking it up.

2.2.3.2. Proving ground (Figure 2)

Any place where there is no significant acoustic disturbance may be used as a test site. In particular, flat surfaces that are covered with concrete, asphalt or another hard material and have a high level of sound reflection are suitable for this purpose; Areas made of firmly rolled earth are excluded. The test site must have at least the dimensions of a rectangle, the sides of which are 3 m away from the outline of the motorcycle (excluding the handlebars). There must be no significant obstacles within this rectangle, for example persons other than the driver and the observer.

The motorcycle must be set up within the aforementioned rectangle in such a way that the measuring microphone is at least 1 m away from any curbs that may be present.

2.2.3.3. miscellaneous

Indications of the measuring device caused by background noises and the influence of wind must be at least 10 dB (A) below the noise level to be measured. A suitable windscreen may be attached to the microphone, provided that its influence on the sensitivity of the microphone is taken into account.

2.2.4. Measurement method

2.2.4.1. Type and number of measurements

During the operational process according to 2.2.4.3 the A-weighted maximum noise level in decibels (dB) is to be measured.

At least three measurements are to be made at each measuring point.

2.2.4.2. Microphone positions (Figure 2)

The microphone is to be set up at the level of the exhaust outlet, but in no case less than 0.2 m above the road surface. The microphone capsule must face the exhaust gas outlet opening and be 0.5 m away from this opening. The axis of greatest sensitivity of the microphone must run parallel to the road surface and form an angle of 45 ° ± 10 ° to the vertical plane in which the direction of exit of the exhaust gases lies.

With reference to this vertical plane, the microphone must be placed on the side that allows the greatest possible distance between the microphone and the outline of the motorcycle (excluding the handlebars). If the exhaust system has several outlets whose center-to-center distance is no greater than 0.3 m, the microphone must be assigned to the outlet that is closest to the outline of the motorcycle (excluding the handlebars) or that is the greatest distance from the road surface. If the center-to-center distance of the mouths is more than 0.3 m, separate measurements are to be made for each mouth, whereby the largest measured value is to be recorded.

2.2.4.3. Operating conditions

The speed of the motor must be kept constant at one of the following values:

-> NUM> S> DEN> 2, if S is greater than 5,000 rpm, -> NUM> 3S> DEN> 4, if S is less than or equal to 5,000 rpm.

"S" stands for the nominal power speed according to Section 3.2.1.7 of Appendix 1 A.

After the constant speed has been reached, the throttle valve actuation device must suddenly be returned to the idle position. The sound level is to be measured during the operating sequence, which includes briefly maintaining the constant speed and the entire duration of the deceleration, with the maximum display value being taken as the measured value.

2.2.5. Results (test report)

2.2.5.1. In the test report for the document according to Annex 1 B, all necessary information, in particular the information relating to the measurement of the stationary noise, must be noted.

2.2.5.2. The measured values ​​are to be read on the measuring device and rounded up or down to the nearest whole decibel.

If the comma is followed by a number between 0 and 4, it is rounded down; if it is followed by a number between 5 and 9, it is rounded up.

Only measured values ​​are to be used whose difference in three consecutive measurements is not greater than 2 dB (A).

2.2.5.3. The highest of these three measured values ​​counts as the measurement result.

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Here is the link to the exact wording of the entire guideline.

By the way, it says something different from what Fischi wrote above:

"After the constant speed has been reached, the throttle valve actuation device must suddenly be returned to the idle position. The sound level is to be measured during the operating sequence, which includes briefly maintaining the constant speed and the entire duration of the deceleration, the maximum display value being taken as the measured value. "

... I can't find the 30m distance to the building spontaneously either.